Telescope.



UNITED sTATEs PATENT OFFICE.

EDWARD BAUSCH, 0F ROCHESTER,

COMPANY, 0F ROCHESTER,

NEW YORK, ASSIGtN' OR T0 BAUSCH & LOMB OPTICAL NEW YORK, A. CORPORATION OF NEW YORK. v

TELESCOPE.

To all whom z't may concern.'

Be it known that I, EDWARD citizen of the yUnited States, residing Rochester, in the county of Monroe, t of New York, have invented certain new and useful Improvements in Telescopes; and I do hereby declare the following to be a full, clear, and exact description of the same, reference being had to the'accompanying drawings, forming a part of this specification, and to the characters of reference marked thereon.

This invention relates to optical instruments and more particularly relates tojoptical instruments embodying a fiducial mark arranged in a focal plane of the instrument. In the optical art it lis not new to arrange a fiducial an instrument, as has been done in a binocular telescope provided with what is known as a mil scalewhich comprises a fiducial scale etched on the surface -of a glass disk and arranged in the field of the ocular. A disadvantage attending use of this prior instrument is that the delicate mil scale is liable to become temporarily obscured or obliterated by -dust or foreign matter which collects on the scale supporting transparent disk or plate. A binocular telescope of the class herein illustrated is peculiarly susceptible to this deposition of dust on the mil scale"or other fiducial mark because the body or casing containing the prism systems is usuallyformedby a casting process which leaves the walls of the interlor rism holding chambers more or less roug and scaly and with various corners or projections which are liable to collect dust after a most careful cleaning. of the parts when first assembling them, and the joint spaces around :the prisms and their fastenings also readily accumulate dust, and this collected dust is shaken off by jars incident to use of the instrument and lodges upon the mil scale support or plate and obscures or obliterates the fduclal mark. l

The main object of this invention is to provide a simple and efiicient means for pre- BAUSQH, a

Venting the veiling or obliteration of a iiducial mark or scale arranged or imaged in the focal plane of an optical instrument, and more particularly a binocular" prism telescope.

In the drawings:

Figure 1 isa sectional elevation of one- Specication of Letters Patent.

Application led April 17, 1916. Serial No. 91,533. 1

at 1 ate mark or scale in the focal' plane of l,

Patented July 2, 1918.

.Fig. 3 is a face view of the transparent.

plate carrying the fiducial mark, and

Figs. 4 and 5 are sectional side views of the unitary mounting carrying the fiducial i mark supporting and dust-guard plates shown in Figs. 1 and 2 respectively.

Similar reference characters throughout the several views indicate the same parts.

Referring now more especially to Fi s.

l to 4 of the drawings, the numeral 1 enotes an objective mounted at the forward end of the field glass body or casing 2 in a suitable detachable mounting 3. An ocular tube 4: is threaded at 5 into the rear end of the body 2 and carries at its outer extremity a suitable mounting 6 in which are fitted a. field lens 7 and an eye lens 8. A ferrule 9 is rigidly' secured to the lens mounting 6, ,and to the outer end of the ferrule is secured the guard 10. The lens mounting 6 has external threads ll-fitting internal threads on the tube 4, and by turning the ferrule 9, the position of the lenses 7, 8, may be adjusted in welllknown manner relatively to the two prisms 12 and 13 which are fittedin the casing 2 and coact to direct the light which passes through the objective 1, into and through the lenses 7 and 8; the optical axis of ,the instrument passing through the objective 1, the prisms 12, 13, and the lenses 7, 8. Both the right hand and lefthand telescope systems of the binocular instrument are identical in structure as thus far described.

The fiducial mark is preferably arranged in the left hand telescope system 0f the binocular and preferably is a mil scale including two graduated linear scales crossing each other centrally at right angles, as shown at 15 in Fig. 3, and indicated by the conventional cross mark 15 in Figs. 1,' 2, 4 and 5 of the drawings. This mil scale is preferably etched into the rear face of a glass plate 16 held within a tubular mounting .17. This mounting has a nearly full length internal screw-thread 18, and near its supporting 4 mounting 17,

V.ens system 7, 8, '-,anobject formed in the plane of the fiducial :mark 15, will clearly appear,

' LjW- it rear end has an external rib 19, and an adj acent external screw thread 20 which screws into aninternal thread of the ocular tube 4, until stopped by contact of the rib 19 with Said tube. on the mounting 17 is preferably beveled at its inner face and the margin of the mil scale late 16 is correspondingly beveled to closely t against the beveled edge of the flange 21, While Lits rear face is ush with br projects slightly beyond this flange to facilitate easy and borough cleaning of the outer face of the mil scale plate after'it is slipped into the wherein it is held securely by an externally threaded collar or sleeve`22 enlgaging the mounting thread 18. A'glass or other transparent dust-guard plate 23 now is slipped into the mounting 17 and rests against the sleeve 22, and a threaded sleeve 24 is then screwed into the mounting thread v18 and against the guard plate 23 to securely lock it in position 'within the mounting 17, and at a distance from the mil scale plate 16 f about one-half the comparatively short .focal length of the ocular lens system 7, 8, ef- .the telescope andv out Vof the focus offfthis lens system. The mil scale sup- `fortilng plate 16 lies in the focus of said and therefore the image of simultaneously the eld of ifo'n of the instrument, and any dust'parles which may chance to adhere to the terfront face of the dust-guard plate 23, 'h is out of focus of the lenses 7, 8, will appreciably affect theclarity of vision :will but slightly reduce the illumina- Experiments have proved that a comvely large opaque object lodged on the fh .the image "of the mark, in

be but faintly seen in thefeld of vision apparently transparent rin color than the field. itself.`

the above described binocular instruthreads 11 of rd to exclude dust from the opposed face of the plate 16 upon which the 'al mark 15 is etched. jany optical instrument whose ocular vhave a sufficiently long focus to give f-for a second independent dust-guard ocated out of the focus of' said lenses, ossible in accordance `with thisinto v use twodust-guard plates, -one .edv oppositeeach .face ofthe mil scale one Example `of such A'modied conctlon shown e prism telescope l 2 and 5 of the j: rumeniI a tubular ting 251 1s internally threaded at 0 parent dust-guard An internal rear end flange 21* dust-guard 32, respectively,

1 front face of the dust-guard plate 23,y

object slightly 4 therein,

this mounting may be` relied upn as' closure plate tached ,to said casing with 'inthe focal planer of the lens system, and transparent closure plate supported in7 saidA mountingjin a plane substantially parallel t'othe planjejof the idducial mark and spaced,

18 at opposite ends has an internal shoulder 26 against which, and out of the focus of the ocular lenses 7, 8, is placed a rear transplate 27, held in place by a sleeve 28. screwed into the rear mounting threads 18. Against another internal shoulder 29 of the mounting 25 rests in the focus of the -lenses 7, 8, a transparent plate" 30 having etched thereon any approved fiducial mark such as the mil scale 1 5 shown in Fig. 3. The mil scale plate 30 is held in position by a second sleeve 31 screwed into the front mounting threads 18. Against the forward end of the sleeve 31 rests a second plate 32 'which is held in position out of the focus of the lenses 7, 8, by a third sleeve 33 screwed into the mountmg threads 18. In this modified .construction the two transparent dust-guard plates 27, oppose opposite faces of the mil scale plate 30, and thus effectively guard against dust veiling or obliteration of the ducial mark independently of the lens system of the instrument. l

In the prism telescopes sufficiently shown in Figs. 1 and 2 Aof the drawings, the mounting carrying the mil scale fducial mark and its dust-guard plate or plates, constitutes a complete unitary structure which may be made in quantities on the system of interchangeable parts, and may be applied to the respective short and long focus telescopes by simply screwing the mounting 17 or 25, at its threads 20 into the forward end of the ocular tube 4, prior to screwing said tube at 5, into the lbody or casing 2 of the instrument.

Having thus described my invention, what I claim and desire to secure by Letters Patent of the United States is:

1. In an optical instrument, the combination with an objective, and an ocular tube closed at one end by an ocular mounted of a tubular mounting having a fiducial mark and a closure plate. mounted therein, in spaced relation to the mark, said mounting being adapted to be attached to the ocular tube at a point between the objective and the ocular with the iducial mark in the focal plane of the ocular and with the beyond said focal plane, out of focus ofthe'ocular.

2. In ah optical instrument, the combinalosed at one end by a tion with a casing c lens system mounted'therem, a mountingl adapted to be atoarrymg a fiducial mark the flducial mark a distancexiappro ting4 halfythe focal 1 length off-61.177.flanks..geraten.brledawlzfsialv 3. In an optical instrument, the combination With an objective and an ocular, of a tubular mounting provided with a transarent closure at ar near each end, and a ducial mark arranged within said mounting in spaced relation -to both of said closures2 said mounting being adapted to be positioned in the path of light between the objective and the ocular with the. fiducial mark in.a focal plane of the instrument and with the exposed surfaces of the closures out of focus.

4. In an optical instrument, the combination with a body or casing, an objective mounted at the forward end of the casing, an ocular tube secured tothe rear end of the casing, a lens system in the ocular tube, and a prism system interposed in the optical axis of the objective and ocular lens systems, of a tubular mounting attached at the forward end of the ocular tube, a transparent plate carrying a iducial mark and held by the mounting in the focal plane of the ocular lens system, a transparent closure' plate held by the mounting and guarding the liducial mark from dust andlocated out of the focus of the, ocular lens system, and means securing the ducial mark carrying plate and the dust-guard closure plate to the mounting in the aforesaid relative positions.

5. In an optical instrument, the combination with a body or casing, an objective mounted at the forward end of the casing, an ocular tube secured to the rear end of the casing, a lens system in the ocular tube, and a rism system interposed in the optical axis o the objective and ocular lens systems, of a tubular mounting attached at the forward and of the ocular tube and having an internal shoulder and internal screw-threads, a transparent plate carrying a iducial mark and placed within the lnounting against its shoulder and in the focal plane of the ocular lens system, a transparent closure plate in the mounting guarding the liducial mark from dust and located out of the focus of the ocular lens system, and sleeve means engaging the internal threads of the mounting and securing the ducial mark carrying plate` plate to thev 50 and the dust-guard closure mounting in the, aforesaid relatlve positions.

EDWARD BAUSCH.

lVitnesses:

CARL F. LoNEL, GUsTAv ERBE. 

